1. Field of the Invention
The present invention relates to a thin film capacitor and a method of manufacturing the same and, more particularly, a thin film capacitor having a high-dielectric capacitor insulating film and a method of manufacturing the same.
2. Description of the Prior Art
The integrated high-dielectric thin film capacitor is employed as the decoupling capacitor that suppresses voltage noises or voltage variation caused in the power bus line, the storage capacitor of DRAM or nonvolatile FRAM (NVFRAM), and the dynamic tunable element in applications of the microwave devices. In these applications, high-dielectric material or ferroelectric material made of any one of the oxide having the perovskite structure such as (Ba,Sr)TiO3 and the compound containing the pyrochlore structure such as Pb2(ZrTi)2O7 is often employed as the material of the capacitor insulating film.
However, major reasons for hesitating the employment of these capacitor insulating films are that the leakage current is large and reliability is low at the time of high voltage application.
The electrical characteristics of the capacitor are strongly affected by film quality of the dielectric film as the capacitor insulating film, particularly the dielectric oxide thin film. In more detail, normally the polycrystalline dielectric oxide thin film has a high relative dielectric constant but has a low breakdown voltage. In contrast, the amorphous dielectric oxide thin film has a low relative dielectric constant but has a high breakdown voltage and a small leakage current. Thus, such thin film can attain the high reliability.
Based on these considerations, in order to compensate the polycrystalline dielectric oxide thin film and the amorphous dielectric oxide thin film for respective demerits, it may be thought of to employ a laminated structure containing both of them. An example of such laminated structure is shown in FIG. 1 as a sectional view. In FIG. 1, 1 is a silicon substrate, 2 is a silicon oxide film, 3 is a first electrode, 4 is an amorphous dielectric oxide thin film, 5 is a polycrystalline dielectric oxide thin film, and 6 is a second electrode.
Such laminated structure can lead to an optimization of the electrical characteristics such as the capacitance, the leakage current, the breakdown voltage, etc. In other words, it can lead to a formation of the capacitor with the high breakdown voltage, the small leakage current, and the available capacitance value.
Such laminating method/laminated structure are set forth in U.S. Pat. Nos. 6,190,924B1 and 6,143,597, and Japanese Patent Application Publications (KOKAI) Hei 05-343254, Hei 09-36309, Hei 11-330391, 2003-31403, etc. According to these prior arts, the laminated structure is obtained by laminating the flat amorphous dielectric thin film and the flat polycrystalline dielectric thin film. The flat amorphous dielectric oxide thin film and the flat polycrystalline dielectric oxide thin film are formed of different film forming material under different film forming conditions respectively.
However, according to this laminating method, since the sufficiently high effective dielectric constant cannot be derived yet and also a variety of film forming conditions and film forming materials are required, it causes a serious problem such that complexity of the production control is increased and thus increase in a production cost is brought about. Also, since the film forming conditions and the film forming materials are different, respective film formations must be carried out while changing the chamber and thus it is possible that the interface between the amorphous dielectric thin film and the polycrystalline dielectric thin film is contaminated.